This invention relates to the new compound t-butylperoxycyclododecyl oxalate, its production and its use as a polymerization initiator.
For the polymerization of unsaturated monomers, especially of vinyl chloride, there is a need for highly reactive initiators which decompose faster than the peroxydicarbonates most frequently used at present, and which thus allow short reaction cycles even at low polymerization temperatures. Admittedly, there are highly reactive initiators already in use, such as ACSP (acetyl cyclohexane sulfonyl peroxide) and CUPND (cumylperoxy neodecanoate), but these initiators have some disadvantages, eg, unpleasantly smelling decomposition products in the case of CUPND, and corrosive properties in the case of ACSP.
An added disadvantage of highly reactive liquid initiators is the necessity of storing and transporting them at low temperatures, generally below xe2x88x9215xc2x0 C.
The EP 271 462 (Kenobel AB) describes esters of monoperoxyoxalic acid which are solid at ambient temperature. These esters are the O-n-alkyl, xe2x80x94OOxe2x80x94 t-alkyl esters of monoperoxyoxalic acid, where the n-alkyl groups are radicals with 18 to 28 C atoms.
The disadvantage of these compounds is that they are wax-like solids. Their active oxygen content is relatively low on account of the high formula weight (eg, 3.23% in the case of n-docosyl tert-butylperoxy oxalate). They have to be produced from long-chain fatty alcohols which do not dissolve well in the necessary non-polar solvents. One therefore requires large quantities of solvent, which subsequently has to be removed by distillation under vacuum.
Other esters of monoperoxyoxalic acid have also been prepared, which are solid at ambient temperature and, because they have a lower formula weight, have a higher active oxygen content. However, there were safety problems due to the compounds"" explosive property and the fact that they are shock sensitive. These undesirable properties are particularly pronounced in the case of bis-tert-butylperoxy oxalate.
The object of this invention consisted in providing an initiator which is solid at ambient temperature and highly reactive when in solution, can be handled safely at temperatures of about +10xc2x0 C., and which does not have the disadvantages of the hitherto known initiators.
The object is established according to the invention by provision of the new t-butylperoxycyclododecyl oxalate. This compound is a crystalline substance which melts at 48xc2x0 C., has an active oxygen content of 4.8% and a half-life of 10 hours at 32xc2x0 C. At 18xc2x0 C., the loss of active oxygen is about 3% relative in a week, which means that the compound can be handled safely at ambient temperature for a certain length of time.
Surprisingly, t-butylperoxycyclododecyl oxalate turns out to be a highly reactive initiator for the polymerization of unsaturated monomers and in particular for the polymerization of vinyl chloride. It decomposes faster than hitherto known initiators and thus allows short reaction cycles even at low polymerization temperatures of xe2x89xa650xc2x0 C.
Additional subject matter of the specification is a method of preparing t-butyl-peroxycyclododecyl oxalate. According to this method, t-butylhydroperoxide is reacted with cyclododecyl oxalyl chloride to form the t-butylperoxycyclodo-decyl oxalate. It is preferable if the t-butylperoxycyclododecyl oxalate is obtained as a crystalline compound which, in the form of a solid substance at ambient temperature, is essentially stable and can thus be stored and transported without the need for costly and time-consuming precautions. When the crystalline t-butylperoxycyclododecyl oxalate is dissolved in a suitable solvent, one obtains a solution of a highly reactive initiator with which unsaturated monomers can be polymerized faster than with initiators used so far. During the polymerization of vinyl chloride at 40 to 45xc2x0 C., the t-butylperoxycyclododecyl oxalate is more reactive than the known initiators CUPND and ACSP.
Also subject matter of the application is the use of t-butylperoxycyclododecyl oxalate as an initiator for the polymerization of unsaturated monomers, in particular of vinyl chloride. However, t-butylperoxycyclododecyl oxalate can also be used as an initiator for other unsaturated monomers, and is suitable, for example, for the production of polyvinyl acetate and LDPE (low-density polyethylene).
The invention is explained in more detail by means of the following examples.